How the tuner works

When you press Start tuner, your browser passes the microphone signal to the page as a stream of audio samples. About twenty times a second the tuner takes the most recent ~85 milliseconds of sound and estimates its fundamental frequency with the YIN algorithm (de Cheveigné & Kawahara, 2002), which compares the waveform with delayed copies of itself to find how often it repeats. That works even when, as with low cello or bass strings, the microphone picks up the overtones more strongly than the fundamental.

Readings are smoothed with a short running median so the needle is steady, and the frequency is converted to the nearest note in twelve-tone equal temperament relative to your chosen reference pitch (A4 = 440 Hz unless you change it). The difference is shown in cents — hundredths of a semitone.

Accuracy

On a clean, sustained note the tuner is accurate to about a cent. Real instruments add vibrato, bow noise and slightly stretched overtones, so expect the needle to move a little; aim to keep it inside the green ±5 cent zone.

Tips for good readings

• Play one string at a time and mute the others.
• Get close to the microphone (around 30 cm / a foot) in a quiet room.
• Pluck or bow evenly and let the note ring.
• For bass instruments, try the 12th-fret harmonic.

Privacy

All processing happens on your device. Nothing you play is recorded or uploaded. See privacy.